This invention relates to liquid polymer compositions which are useful in the manufacture of imaged printing plates and coatings through photopolymerization. Photocurable compositions useful in forming printing plates and coatings, in general, are well known in the art. In particular U.S. Pat. No. 2,760,863 (Plambeck) describes the use of certain photopolymers in the fabrication of printing plates. However, the processes of Plambeck require the use of relatively toxic solvents to develop away the unpolymerized photopolymer thereby revealing the relief image of the printing plate.
U.S. Pat. Nos. 3,960,572; 4,137,081; 4,442,302; and 4,857,434, the teaching each of which are included herein by reference in their entirety, reveal certain improvements to the processes of Plambeck. One of the most notable improvements of the foregoing disclosures is that the photopolymers utilized can be developed, after selective polymerization with light, in aqueous based solutions. Aqueous developable photopolymers of the foregoing type are currently marketed under the Merigraph trade name by MacDermid Imaging Technology, Inc. of Wilmington, Del. These aqueous developable photopolymers are useful in printing a variety of substrates including paper, cardboard and plastic, due to the fact that they are capable of forming printing plates having the necessary hardness, flexibility, resilience, and abrasion resistance required for such printing.
The liquid photopolymers currently known and utilized are generally useful in printing with aqueous based inks only. They are not useful in printing with polar organic solvent based inks, such as alcohol based inks, because the cured polymers do not possess the necessary resistance to polar solvents. When exposed to polar solvent based inks cured liquid photopolymers generally degrade or swell to an unacceptable degree, making their usefulness in printing these inks much less than desirable.
In a variety of applications, such as film printing, it is necessary or desirable to print with polar solvent based inks. The solvents used in such inks may be one or a mixture of commonly used organic solvents, such as isopropyl alcohol and n-propyl acetate. In any case, liquid photopolymers, such as those described above, have not possessed the necessary resistance to these polar solvents and thus are not useful in fabricating printing plates for these applications.
It is therefore an object of this invention to reveal liquid photopolymer compositions which produce printing plates which are resistant to a variety of inks, including water based, alcohol based and hydrocarbon based inks. The printing plates produced using the compositions of this invention are therefore useful in a wide variety of printing applications.
It is a further object of this invention to reveal liquid photopolymer compositions which produce printing plates having the hardness, flexibility and abrasion resistance which is necessary for printing in a variety of applications. Thus the photopolymer compositions of this invention are capable of producing high quality artwork using a wide variety of inks and on various types of surfaces.